The correct answer is - rainfall.
The Ogallala Aquifer is a very large aquifer. It traces its origins at the end of the last ice age, where the water from the melting glaciers filled it up. After that initial filling of from the water of melting glaciers, the Ogallala Aquifer has been reliant on the water from the rainfall to fill it, and replenish the lost water.
Since the humans started to use it though, this aquifer has been constantly experiencing decrease in its water levels. The reason for that is that the humans use more water from the aquifer than what the rainfall can replenish, and that is especially a big problem because the aquifer is located in an area where there isn't a lot of precipitation.
Oil reserves are the amount of technically and economically recoverable oil. Reserves may be for a well, for a reservoir, for a field, for a nation, or for the world. Different classifications of reserves are related to their degree of certainty.
The total estimated amount of oil in an oil reservoir, including both producible and non-producible oil, is called oil in place. However, because of reservoir characteristics and limitations in petroleum extraction technologies, only a fraction of this oil can be brought to the surface, and it is only this producible fraction that is considered to be reserves. The ratio of reserves to the total amount of oil in a particular reservoir is called the recovery factor. Determining a recovery factor for a given field depends on several features of the operation, including method of oil recovery used and technological developments.[1]
The answer is “During the reign of Askia Muhammad, the Songhai
empire reached its greatest size.”
<span>Askia is also known as Muhammad Ture. He was able to extend
the territory of the Songhai Empire. He was able to get alliances, thus allowed
him to easily conquer many kingdoms. One of the achievements of the Songhai
empire, he was able to gain the respect of his people.</span>
